1. Field of the Invention
The present invention relates to equipment and a method for painting a fuel tank and the like for use in a motorcycle.
2. Description of the Prior Art
Equipment for painting a fuel tank for use in a motorcycle is known in the prior art. For example, in Japanese Utility Model Publication No. Hei 4-4844, painting is performed by rotating a support member for supporting a workpiece around its axis to prevent paint applied to a painting surface from dripping and forming a non-uniform paint film. Further, as shown in FIG. 9, in a method for providing a conveyance device 52 for a workpiece W within a spray-booth 51, there is the possibility that paint to be sprayed onto the workpiece W will adhere to a conveyer or the like of the conveyance device 52 and some paint peeling off from the conveyer may adhere to the workpiece W, thereby causing inferior painting. To avoid such a problem, in Japanese Unexamined Patent Publication No. Hei 6-134360, only a supporting rod for supporting the workpiece is inserted into the spray booth and a means for moving the supporting rod is arranged outside the spray booth.
However, according to the conventional painting methods, since the workpiece is always moved during painting, it is difficult to raise the painting quality and the like to more than a fixed level. Further, to improve the painting quality beyond a certain extent, there is a problem that equipment construction becomes complicated and large.
It is therefore an object of the present invention to provide painting equipment of which the construction is compact and which can improve the painting quality and the like.
To attain the above-mentioned object, according to the present invention, painting equipment in which a workpiece is fed to functional processing stations in order, by a conveyance device to perform a series of operations from coating to baking and drying is provided, characterized in that the conveyance device comprises a shuttle feed mechanism for conveying a conveyance frame for supporting the workpiece using a shuttle feeding method from upstream functional processing stations toward downstream functional processing stations, and a self-propelled mechanism for allowing the conveyance frame to cyclically travel from the downstream functional processing stations to the upstream functional processing stations by itself.
In this manner, if the workpiece is conveyed to the functional processing stations, in order, using the shuttle feeding method and once conveyance is completed, movement of the work is stopped to perform painting, baking, drying, etc., it is possible to perform high quality painting and the like.
The functional processing stations include a painting station for performing the painting, a setting station for removing solvents etc., a preheating station for preheating, a UV baking station for baking the paint, an after-heating station for drying a paint film, and the like.
After a series of operations is completed, the workpiece is removed from the conveyance frame. The conveyance frame is then fed into the self-propelled mechanism to allow the conveyance frame to travel by itself and return to the upstream functional processing station for circulation. Thus, it is possible to make the entire equipment construction compact.
To allow the conveyance frame to travel by itself, a slope can be provided, for example, on a floor to make the construction inexpensive.
The conveyance frame is composed of a carriage which travels outside a booth for each functional processing station and a workpiece supporting arm which is supported by the carriage and extends to the inside of the booth, wherein the workpiece supporting arm is rotatably provided around an arm axis by a rotational mechanism.
In this manner, if the carriage for supporting the workpiece supporting arm is provided outside the booth, it is possible to prevent paints from adhering to a conveyance driving section and prevent some paint peeling off from the conveyance driving section from adhering to the workpiece, thereby causing inferior painting.
Further, by spraying the paint on the workpiece and rotating the workpiece supporting arm, it is possible to prevent the paint from dripping to provide a uniform painting film and to improve the painting quality further.
A self-propelled feed passage used as a return passage is provided with a downward slope toward a workpiece supply section side to allow the conveyance frame to return to the workpiece supply section side from its own weight.
A rotational positioning mechanism is provided on the downstream side of the functional processing stations to control a rotational position of the workpiece supporting arm at a fixed location.
By having the direction of the workpiece supporting arm fixed by this rotation positioning mechanism, it is possible to make the removal of the workpiece from or the setting of the next workpiece into the workpiece supporting arm easier.
The mechanism for rotating the workpiece supporting arm around the arm axis is composed of a chain provided along the shuttle feed passage, and a sprocket which engages a section of the chain travelling in the opposite direction from the travelling direction of the conveyance frame and transmits a driving force to the axis of the workpiece supporting arm. Accordingly, it is possible to rotate the workpiece supporting arm with certainty and by a simple mechanism.
The above and other objects, features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings.